2-pass commissioning

From HallCWiki
Jump to: navigation, search

Beam Commissioning at 2-pass for Fall 2019

The main purpose of 2-pass commissioning is to establish beam in hall, raster condition, and commission the target. We probably do not need beam energy and BCM calibrations at this stage. No beam polarization is needed.

This plan also works for 1-pass commissioning (if 2-pass is not available)

You can find an high-level overview of the run plan here.

Polarized_Helium-3_Experiments#Run_Plan <- click this to return to main run plan page

Beam checkout (Full Procedure after Accelerator Down)

For polarized 3He running in Fall 2019 and Spring 2020, the nominal raster for production is 5mm diameter circular. The nominal triggers used are 3/4 for both HMS and SHMS. No coincidence trigger will be used/setup.

Establish beam in the hall and Raster Checkout (Long Procedure)

 Please refer to Beam and Raster Checkout for A1n/d2n (Long Procedure).
 Spectrometers can be set at the angle and momentum for the next step (30deg).
 Pol3He cell can be set at 0-deg direction.   Please refer to Target Field Runplan for coil currents needed by the polarized 3He target field.

BCM Calibration

 Goals 
 - BCM Calibration
 Procedure
 - Follow draft instructions here: Non-invasive BCM calibration procedure for 3He running 2019-2020

Target system checkout and commissioning (30min or as long as needed)

 Goals 
 - Make sure we can put beam on all targets. Raster should be ON (5mm diameter) for all settings.
 - This step also serves/completes the basic trigger/DAQ checkout, and tuning of online monitoring scripts.
 - Have a rough feeling for large ytarg optics.
 Setup for 2-pass
 - Beam Current:   5-30 uA CW, raster always ON (5mm diameter)
 - HMS setting: 30 deg, -1.60793 GeV (electron W=2)
 - SHMS setting: 30 deg, -1.60793 GeV (electron W=2)
 - Target:      Varies (All except Polarized 3He Cell)
 - 
 Alternate Setup for 1-pass
 - Beam Current:   5-30 uA CW, raster always ON (5mm diameter)
 - HMS setting: 30 deg, -1.40526 GeV (electron W=1.232)
 - SHMS setting: 30 deg, -1.40526 GeV (electron W=1.232)
 - Target:         Varies (All except Polarized 3He Cell)
 Procedure
 - Move target to (Single) Carbon foil position, take a 2 minute run at 5 uA and confirm we see two foils.
 - Keep target at (Single) Carbon foil position, ask MCC to increase current to 30 uA for one minute, verify ramp rate is no more than 1uA/sec and that beam reach 30uA.
 - Move target to Optics Target (multi-carbon foil) position, take a 2 minute run at 5 uA and confirm we see all seven foil.
 - Fill reference cell with 1 atm N2, verify raster is really ON.
 - Move target to Reference Cell position, start a run at 5uA, increase current to 10uA, 15uA, 20uA, 25uA, and 30uA, stay 2 minute at each current setting. Look for the two glass windows at (nominally) z=+20 and -20cm and verify target is still there.
 Things to look for
 - for 1atm N2 Reference Cell, count rate should be roughly (0.5-1.0)Hz per uA of current.
 - for 1atm N2 Reference Cell, event count from each glass window (150um) should be 40% of that from the N2 gas (40cm 1atm). This means we should see windows in ytar or ztar histogram even though ytarg reconstruction at the extended position is not optimized.

Polarized 3He Cell checkout and commissioning (30min minimum, up to 8 hours if measuring depolarization)

 Goals 
 - Make sure we can put beam on the polarized 3He cell.
 - This should also complete the commission of all target polarimetry.
 - Make sure Target Spin can be set at all 4 directions: 0, 90, 180 and 270 deg.
 - Ideally we would like to determine beam depolarization effect and time constant.
 - Optimize target FOM by varying beam current (optional).
 Setup for 2-pass
 - Beam Current: 5-30 uA CW, raster always ON (5mm diameter)
 - HMS setting:  30 deg, -1.60793 GeV (electron W=2)
 - SHMS setting: 30 deg, -1.60793 GeV (electron W=2)
 - Target:       Polarized 3He Cell
 - 
 Alternate Setup for 1-pass
 - Beam Current: 5-30 uA CW, raster always ON (5mm diameter)
 - HMS setting:  30 deg, -1.40526 GeV (electron W=1.232)
 - SHMS setting: 30 deg, -1.40526 GeV (electron W=1.232)
 - Target:       Polarized 3He Cell
 Pol 3He Target Setup
 - Target spin direction: mostly 0 and 180 deg, may also use 90 and 270 deg.
 - See Target Field Runplan for coil currents settings.
 Procedure for Commission Target Polarimetry (Varies)
 - Target experts will do this
 - Please make sure target spin can be rotated to all 4 directions: 0 (downstream), 90 (beam left), 180 (upstream) and 270 (beam right) deg. 
 Procedure for Commission Polarized 3He Target Cell (30min)
 - Set the polarized 3He Target spin in 0 deg.
 - Ask the target operator to do one full set of target polarization measurement: NMR, EPR and PNMR.
 - Move target to polarized 3He cell position, take a 2 minute run at 5uA and confirm we see events from both 3He gas and two glass windows at (nominally) z=+20 and -20cm.
 - Ask MCC to increase current to 10uA, 15uA, 20uA, 25uA, and 30uA, stay 2 minute at each current setting. Watch the beam ramp rate (confirm it is no faster than 1uA/sec), and watch the rate to make sure it roughly scales with current.
 - At 30uA, take one 10-minute run, ask the target operator to do one full set of target polarization measurement: NMR, EPR and PNMR.


 Procedure for Studying Beam Depolarization Effect (6 hours, optional)
 - At 30uA, take 30-minute long runs, ask the target operator to do target polarization measurements: pNMR once every hour, EPR and NMR every 2-3 hours.
 - Stay here for six hours total (beam depolarization time constant is 3-5 hours.)
 - Ask the target operator to do target polarization measurement with all 3 methods: NMR, EPR and PNMR.
 Things to look for
 - for 10atm STP 3He gas, we expect (20-30)Hz event count from 3He gas alone for HMS and 50% higher on SHMS, at 30uA of current.
 - Event count from glass windows (150um each) is expected to be half of that from 3He gas (10atm STP), per window. This means we should see windows in ytar or ztar histogram even though ytarg reconstruction at the extended position is not optimized.

Detector checkout and calibrations

 Goals 
 - to verify PID detectors work properly
 - Calorimeter calibration?
 Procedure
 - Because we use 3/4 triggers, PID and ECal calibrations are not crucial at this stage. However, we can use data taken above to do a rough PID performance check for both the Cherenkov and the ECal.

Possible 2-Pass Optics (angle and ytarg) Calibration (Optional)

 Goals 
 - To calibrate spectrometer optics for 40cm long target at 30 deg. Calibrate angle reconstruction. Note: existing Hall C optics data is not sufficient to cover the 40-cm long extended target of A1n/d2n
 - Note: this calibration can be done at either 2-pass or 1-pass.
 - Time: 8 hour data taking plus configuration changes and short runs to verify setup.
 Setup
 - Beam Current: 5-40 uA CW, raster varies
 - HMS setting:  30 degrees, -2.0 GeV/c (electron)
 - SHMS setting: 30 degrees, -2.0 GeV/c (electron)
 - Target:       Optics Target (Multi-foil Carbon)
 Procedure
 - Move target to Optics Target (multi-carbon foil) position;
 - Move Sieve Slit IN for both HMS and SHMS;
 - Ask 40uA raster OFF, verify trigger rate and set prescale factors (SAVE prescale file before start the new run);
 - Take a short run to verify sieves are both IN;
 - Take eight 30-minute runs (assuming 50% beam quality i.e total 2 hours "beam ON" time) at this setting. 
 - Ask MCC to turn raster ON to 5mm diameter, take four 30-min run at 40 uA (total 1 hour "beam ON" time).
 - Move Sieve Slit OUT for both HMS and SHMS;
 - Take one run at 40 uA (raster OFF) for 30 minutes (15 min "beam ON" time). Check trigger rate and prescale if necessary (If changing PS factors, Must Save file and restart a new run).
 - Ask MCC to turn raster ON to 5mm diameter, take one run for 30 minutes (15 min "beam ON" time) at the same condition. 
 Things to watch for (Expert Analysis)
 - There should be optics expert(s) checking data quality as we go.

Possible Moller

 - no longer an option due to cryo leak in Moller.

Other

 Goals 
 - What to do if we have finished all above and there is still time left before pass change to 1-pass?
 Procedure
 - N/A